CN112352468A

CN112352468A - Induction heating cooker

Info

Publication number: CN112352468A
Application number: CN201880093309.6A
Authority: CN
Inventors: 菅郁朗; 吉野勇人
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 2018-06-14
Filing date: 2018-06-14
Publication date: 2021-02-09
Anticipated expiration: 2038-06-14
Also published as: EP3809801B1; JPWO2019239557A1; JP7038812B2; WO2019239557A1; US20210243853A1; CN112352468B; US11910511B2; EP3809801A1; EP3809801A4

Abstract

The induction heating cooker of the invention comprises: a plurality of heating coils including an inner circumferential coil disposed on an innermost circumferential side and an outer circumferential coil disposed on an outermost circumferential side; and a support base disposed below the plurality of heating coils and supporting the plurality of heating coils, the support base being formed of a non-magnetic flat plate, and the support base having a plurality of openings formed below the outer peripheral coil.

Description

Induction heating cooker

Technical Field

The present invention relates to an induction heating cooker having a plurality of heating coils.

Background

The conventional induction heating cooker includes a heating coil unit. The heating coil unit includes: a heating coil; an insulating plate provided on a lower surface side of the heating coil; ferrite (ferrite) disposed under the insulating plate; and a shield plate mounted on the outer contour and having a ferrite placed thereon. The shield plate is made of a nonmagnetic metal such as aluminum. The shield plate functions as a heating coil support member (see, for example, patent document 1).

Documents of the prior art

Patent document

Patent document 1: international publication No. 2014/156010

Disclosure of Invention

Problems to be solved by the invention

Among the objects to be heated by the induction heating cooker, there are objects to be heated formed of a composite material in which a metal of a magnetic body is attached to a metal of a non-magnetic body. For example, there is a metal-bonded frying pan in which a magnetic material such as stainless steel is bonded to the central portion of the bottom of a non-magnetic aluminum frying pan. In general, a magnetic body is attached to a non-magnetic material to be heated at a central portion where a bottom surface is flat, and a magnetic body is not attached to a curved outer peripheral portion of the bottom surface. When an object to be heated made of a composite material is inductively heated by a plurality of heating coils, a heating operation is performed in which the frequency of a high-frequency current supplied to an outer coil disposed on the outer circumferential side among the plurality of heating coils is higher than the frequency of a high-frequency current supplied to an inner coil disposed on the inner circumferential side. By such a heating operation, induction heating suitable for the material of the object to be heated can be performed.

However, in the induction heating cooker described in patent document 1, a support base (shield plate) made of a nonmagnetic metal is provided below the heating coil. Therefore, in the induction heating cooker described in patent document 1, when the heating operation suitable for the object to be heated made of the composite material as described above is performed, there are the following problems: an eddy current is generated in the support base, and the temperature of the support base rises.

The present invention has been made to solve the above-described problems, and an induction heating cooker in which a temperature increase of a supporting base of a nonmagnetic material can be suppressed is obtained.

Means for solving the problems

The induction heating cooker of the invention comprises: a plurality of heating coils including an inner circumferential coil disposed on an innermost circumferential side and an outer circumferential coil disposed on an outermost circumferential side; a support base disposed below the plurality of heating coils and supporting the plurality of heating coils; a plurality of inverter circuits that supply high-frequency power to the plurality of heating coils, respectively; and a control device that controls driving of the plurality of inverter circuits and performs a heating operation in which a frequency of a high-frequency current supplied to the outer periphery coil is higher than a frequency of a high-frequency current supplied to the inner periphery coil, wherein the support base is formed of a flat plate of a non-magnetic material, and a plurality of openings are formed below the outer periphery coil.

Effects of the invention

In the present invention, the support base is formed of a flat plate of a non-magnetic material, and a plurality of openings are formed in the support base below the outer peripheral coil. Therefore, the temperature rise of the support base can be suppressed.

Drawings

Fig. 1 is an exploded perspective view showing an induction heating cooker according to embodiment 1.

Fig. 2 is a plan view showing a first induction heating member of an induction heating cooker according to embodiment 1.

Fig. 3 is a block diagram showing a configuration of an induction heating cooker according to embodiment 1.

Fig. 4 is a diagram showing a drive circuit of an induction heating cooker according to embodiment 1.

Fig. 5 is a vertical sectional view showing a first induction heating member of an induction heating cooker according to embodiment 1.

Fig. 6 is a plan view showing a support base of an induction heating cooker according to embodiment 1.

Fig. 7 is a plan view showing a support base and ferrite of an induction heating cooker according to embodiment 1.

Fig. 8 is a characteristic diagram for material quality determination based on the relationship between the coil current and the input current in the induction heating cooker according to embodiment 1.

Fig. 9 is a diagram showing an object to be heated of a composite body inductively heated by the induction heating cooker of embodiment 1.

Fig. 10 is a diagram showing a heating coil and an object to be heated in the induction heating cooker according to embodiment 1.

Fig. 11 is a diagram showing a heating coil and an object to be heated in the induction heating cooker according to embodiment 1.

Fig. 12 is a vertical sectional view showing a first induction heating member in modification 1 of the induction heating cooker according to embodiment 1.

Fig. 13 is a plan view showing a support base in modification 2 of the induction heating cooker of embodiment 1.

Fig. 14 is a diagram showing a heating coil and an object to be heated in modification 2 of the induction heating cooker according to embodiment 1.

Fig. 15 is a plan view showing a support base of an induction heating cooker according to embodiment 2.

Fig. 16 is a plan view showing a support base and ferrite of an induction heating cooker according to embodiment 2.

Fig. 17 is a plan view showing a support base and ferrite of an induction heating cooker according to embodiment 3.

Fig. 18 is a vertical sectional view showing a first induction heating member of an induction heating cooker according to embodiment 3.

Fig. 19 is a vertical sectional view showing a first induction heating member in modification 2 of the induction heating cooker of embodiment 3.

Fig. 20 is a vertical sectional view showing a first induction heating member in modification 3 of the induction heating cooker of embodiment 3.

Fig. 21 is a vertical sectional view showing a support base and a magnetism preventing member of an induction heating cooker according to embodiment 4.

Fig. 22 is a vertical sectional view showing a support base and a magnetism preventing member in modification 1 of the induction heating cooker according to embodiment 4.

Fig. 23 is a perspective view showing a support base and a magnetism preventing member in modification 1 of the induction heating cooker according to embodiment 4.

Fig. 24 is a vertical sectional view showing a support base and a magnetism preventing member in modification 2 of the induction heating cooker according to embodiment 4.

Fig. 25 is a perspective view showing a support base and a magnetism preventing member in modification 3 of the induction heating cooker according to embodiment 4.

Fig. 26 is a block diagram showing a configuration of an induction heating cooker according to embodiment 5.

Fig. 27 is a plan view showing a first induction heating member in modification 1 of the induction heating cooker according to embodiment 5.

Fig. 28 is a block diagram showing a configuration of an induction heating cooker according to variation 2 of embodiment 5.

Detailed Description

Embodiment 1.

As shown in fig. 1, a top plate 4 on which an object 5 to be heated such as a pan is placed is provided on an upper portion of an induction heating cooker 100. The top plate 4 is provided with a first induction heating port 1 and a second induction heating port 2 as heating ports for inductively heating the object 5. The first induction heating port 1 and the second induction heating port 2 are arranged side by side in the lateral direction on the near side of the top plate 4. The induction heating cooker 100 according to embodiment 1 further includes a third induction heating port 3 as a heating port of the third port. The third induction heating port 3 is provided at the back side of the first induction heating port 1 and the second induction heating port 2 and at the substantially center position in the lateral direction of the top plate 4.

A first induction heating member 11, a second induction heating member 12, and a third induction heating member 13 for heating the object 5 placed on the heating ports are provided below the first induction heating port 1, the second induction heating port 2, and the third induction heating port 3, respectively. Each heating member is constituted by a coil (see fig. 2).

The entire top plate 4 is made of a material that transmits infrared rays, such as heat-resistant tempered glass or crystallized glass. Further, a circular pot position indication indicating a substantial placement position of the pot is formed on the top plate 4 by coating or printing of paint in accordance with the heating ranges of the first induction heating member 11, the second induction heating member 12, and the third induction heating member 13.

An operation unit 40 is provided on the front side of the top plate 4 as an input device for setting input power and a cooking menu when the object to be heated 5 and the like are heated by the first induction heating member 11, the second induction heating member 12, and the third induction heating member 13. In embodiment 1, three operation units 40 are provided for each induction heating coil.

In addition, a display unit 41 that displays the operating state of each induction heating coil, the input from the operation unit 40, the operation content, and the like is provided as notification means in the vicinity of the operation unit 40. In embodiment 1, three display units 41 are provided for each induction heating coil.

The operating unit 40 and the display unit 41 are not particularly limited, and may be provided for each induction heating member as described above, or may be provided as a member common to the induction heating members. Here, the operation unit 40 is configured by, for example, a mechanical switch such as a push switch or a tactile switch, a touch switch that detects an input operation by a change in electrostatic capacitance of an electrode, or the like. The display unit 41 is configured by, for example, an LCD and an LED.

The operation unit 40 and the display unit 41 may be an operation display unit 43 integrally configured with each other. The operation display unit 43 is constituted by, for example, a touch panel in which touch switches are arranged on the upper surface of an LCD. The LCD is an abbreviation for a Liquid Crystal Device (Liquid Crystal display Device). In addition, the LED is an abbreviation of Light Emitting Diode (LED).

Inside induction heating cooker 100, there are provided: a drive circuit 50 that supplies high-frequency power to the coils of the first induction heating member 11, the second induction heating member 12, and the third induction heating member 13; and a control device 45 for controlling the operation of the entire induction heating cooker including the drive circuit 50.

By supplying high-frequency power to the first induction heating member 11, the second induction heating member 12, and the third induction heating member 13 by the drive circuit 50, a high-frequency magnetic field is generated from the coil of each induction heating member. The detailed configuration of the drive circuit 50 will be described later.

The first induction heating member 11, the second induction heating member 12, and the third induction heating member 13 are configured, for example, as follows. The first induction heating member 11, the second induction heating member 12, and the third induction heating member 13 have the same configuration. Therefore, the structure of the first induction heating member 11 is representatively described below.

The first induction heating member 11 is configured such that a plurality of annular coils having different diameters are concentrically arranged. In fig. 2, the first induction heating member 11 shows a 3-fold loop-shaped coil. The first induction heating member 11 has: an inner peripheral coil 111 disposed at the center of the first induction heating port 1; an intermediate coil 112 disposed on the outer peripheral side of the inner coil 111; and an outer circumferential coil 113 disposed on the outer circumferential side of the intermediate coil 112. That is, the inner peripheral coil 111 is disposed on the innermost peripheral side. The outer coil 113 is disposed on the outermost periphery. The intermediate coil 112 is disposed between the inner coil 111 and the outer coil 113.

The inner coil 111, the intermediate coil 112, and the outer coil 113 are formed by winding a conductive wire made of a metal having an insulating coating. As the conductive wire, for example, any metal such as copper or aluminum can be used. Further, a lead wire is independently wound around each of the inner coil 111, the intermediate coil 112, and the outer coil 113.

In the following description, the inner coil 111, the intermediate coil 112, and the outer coil 113 may be collectively referred to as a plurality of heating coils.

As shown in fig. 3, the first induction heating member 11 is drive-controlled by a drive circuit 50a, a drive circuit 50b, and a drive circuit 50 c. That is, the inner coil 111 is driven and controlled by the drive circuit 50 a. The intermediate coil 112 is driven and controlled by the drive circuit 50 b. In addition, the outer circumferential coil 113 is driven and controlled by the drive circuit 50 c. When a high-frequency current is supplied from the drive circuit 50a to the inner coil 111, a high-frequency magnetic field is generated from the inner coil 111. When a high-frequency current is supplied from the drive circuit 50b to the intermediate coil 112, a high-frequency magnetic field is generated from the intermediate coil 112. When a high-frequency current is supplied from the drive circuit 50c to the outer-periphery coil 113, a high-frequency magnetic field is generated from the outer-periphery coil 113.

The control device 45 is constituted by dedicated hardware or a CPU that executes a program stored in the memory 48. The control device 45 includes a material determination unit 46 that determines the material of the object 5 placed above each of the inner coil 111, the intermediate coil 112, and the outer coil 113. The CPU is an abbreviation of Central Processing Unit (CPU). The CPU is also referred to as a central processing unit, a processing unit, an arithmetic unit, a microprocessor, a microcomputer, or a processor.

When the control device 45 is dedicated hardware, the control device 45 corresponds to, for example, a single circuit, a composite circuit, an ASIC, an FPGA, or a device in which these are combined. Each of the functional units realized by the control device 45 may be realized by separate hardware, or may be realized by one piece of hardware. The ASIC is an abbreviation of an Application Specific Integrated Circuit (ASIC). In addition, the FPGA is an abbreviation of Field-Programmable Gate Array (FPGA).

When the control device 45 is a CPU, each function executed by the control device 45 is realized by software, firmware, or a combination of software and firmware. Software and firmware are described as programs and are stored in the memory 48. The CPU reads and executes the program stored in the memory 48 to realize each function of the control device 45. Here, the memory 48 is a nonvolatile or volatile semiconductor memory such as a RAM, a ROM, a flash memory, an EPROM, and an EEPROM.

It should be noted that a part of the functions of the control device 45 may be implemented by dedicated hardware, and a part of the functions may be implemented by software or firmware. Note that the RAM is an abbreviation of Random Access Memory (Random Access Memory). The ROM is an abbreviation for Read Only Memory (ROM). EPROM is an abbreviation of Erasable Programmable Read Only Memory (Erasable Programmable Read Only Memory). The EEPROM is an Electrically Erasable Programmable Read-Only Memory (EEPROM).

The drive circuit 50 is provided for each heating member, but the circuit configuration may be the same or may be changed for each heating member. Fig. 4 illustrates a drive circuit 50a for driving the inner coil 111.

As shown in fig. 4, the drive circuit 50a includes a dc power supply circuit 22, an inverter circuit 23, and a resonant capacitor 24 a.

The input current detection means 25a is constituted by, for example, a current sensor, detects a current input from the ac power supply 21 to the dc power supply circuit 22, and outputs a voltage signal corresponding to the input current value to the control device 45.

The dc power supply circuit 22 includes a diode bridge 22a, a reactor 22b, and a smoothing capacitor 22c, converts an ac voltage input from the ac power supply 21 into a dc voltage, and outputs the dc voltage to the inverter circuit 23.

In the inverter circuit 23,

IGBTs

23a and 23b as switching elements are connected in series with the output of the dc power supply circuit 22. In the inverter circuit 23, a diode 23c and a diode 23d as freewheeling diodes are connected in parallel to the IGBT23a and the IGBT23b, respectively. The inverter circuit 23 is a so-called half-bridge type inverter.

The IGBT23a and the IGBT23b are on/off driven by a drive signal output from the control device 45. The controller 45 turns off the IGBT23b while turning on the IGBT23a, and turns on the IGBT23b while turning off the IGBT23a, and outputs a drive signal for alternately turning on and off. Thus, the inverter circuit 23 converts the direct current output from the direct current power supply circuit 22 into a high-frequency alternating current of about 20kHz to 100kHz, and supplies power to the resonance circuit including the inner coil 111 and the resonance capacitor 24 a.

The resonance capacitor 24a is connected in series with the inner peripheral coil 111, and the resonance circuit has a resonance frequency corresponding to the inductance of the inner peripheral coil 111 and the capacitance of the resonance capacitor 24 a. When the object 5 to be heated as a metal load is magnetically coupled, the inductance of the inner peripheral coil 111 changes according to the characteristics of the metal load, and the resonance frequency of the resonance circuit changes according to the change in the inductance.

With the above configuration, a high-frequency current of about several tens of a flows through the inner coil 111. The object 5 to be heated placed on the top plate 4 directly above the inner peripheral coil 111 is inductively heated by the high-frequency magnetic flux generated by the high-frequency current flowing through the inner peripheral coil 111.

The IGBT23a and the IGBT23b as the switching elements are made of, for example, a semiconductor made of a silicon-based material, but may be made of a wide bandgap semiconductor such as silicon carbide or a gallium nitride-based material.

By using a wide bandgap semiconductor for the switching element, the conduction loss of the switching element can be reduced. Further, since heat dissipation from the drive circuit 50a is good even when the drive frequency is high, that is, even when the switch is switched at a high speed, the heat sink of the drive circuit 50 can be made small, and the drive circuit 50a can be made small and low in cost.

The coil current detection member 25b is connected to a resonance circuit including the inner peripheral coil 111 and the resonance capacitor 24 a. The coil current detection means 25b is, for example, a current sensor, detects a current flowing through the inner circumferential coil 111, and outputs a voltage signal corresponding to a coil current value to the control device 45.

In fig. 4, the drive circuit 50a for driving the inner coil 111 is described, but the same configuration can be applied to the drive circuit 50b for driving the intermediate coil 112 and the drive circuit 50c for driving the outer coil 113.

Although fig. 4 shows a half-bridge drive circuit, a full-bridge drive circuit including four IGBTs and four diodes may be used. Further, the drive circuit 50a and the drive circuit 50b may be configured by a full-bridge drive circuit, and a set of arms including two switching elements connected in series between positive and negative bus bars and diodes connected in antiparallel with the switching elements may be shared.

Fig. 7 is a plan view showing a support base and ferrite of an induction heating cooker according to embodiment 1. Fig. 5 to 7 schematically illustrate the arrangement and shape of each component.

As shown in fig. 5, an insulator 60 is disposed below the inner coil 111, the intermediate coil 112, and the outer coil 113. A plurality of ferrites 61 are disposed below the insulator 60. A support base 62 is disposed below the plurality of ferrites 61.

The insulator 60 is made of mica, for example. The insulator 60 is formed in a flat plate shape. The plurality of ferrites 61 are formed in a rod shape, for example. For example, as shown in fig. 7, 8 ferrites 61 are arranged radially from the center of the plurality of heating coils.

The support base 62 supports the plurality of ferrites 61, the insulator 60, the inner coil 111, the intermediate coil 112, and the outer coil 113. The support base 62 is made of a non-magnetic material. The support base 62 is made of a non-magnetic metal such as aluminum or non-magnetic stainless steel. The support table 62 is formed in a flat plate shape. The support base 62 functions as a shield for suppressing leakage of the magnetic field from the plurality of heating coils downward. The support base 62 functions as a heat sink for radiating heat from the plurality of heating coils.

The support base 62 has an annular portion 62a formed by projecting an end portion of the outer periphery upward. The annular portion 62a functions as a shield that suppresses leakage of magnetic flux from the plurality of heating coils to the side. The annular portion 62a may be formed separately from the support base 62. In addition, the annular portion 62a may be omitted.

The support base 62 has a plurality of openings 63 formed below the outer peripheral coil 113. As shown in fig. 6, the plurality of openings 63 are formed in a rectangular shape, for example. The shape of the plurality of openings 63 is not limited to a rectangle, and may be any shape such as a circle or an ellipse. In addition, the plurality of openings 63 may be provided below the ferrite 61.

Next, the operation of the induction heating cooker of embodiment 1 will be described.

When the user places the object 5 on the heating port and instructs the operation display unit 43 to start heating (input of heating power), the material determination unit 46 of the control device 45 performs the material determination process.

As shown in fig. 8, the relationship between the coil current and the input current differs depending on the material of the load placed above each of the inner coil 111, the intermediate coil 112, and the outer coil 113. The control device 45 stores in advance a material determination table in which the relationship between the coil current and the input current shown in fig. 8 is tabulated in the memory 48.

In the material quality determination process, the control device 45 drives the inverter circuit 23 with a specific drive signal for material quality determination for each of the drive circuits 50a to 50c, and detects the input current from the output signal of the input current detection means 25 a. At the same time, the control device 45 detects the coil current based on the output signal of the coil current detection means 25 b. The material determination unit 46 of the control device 45 determines the material of the load placed above the coil based on the detected coil current and input current and a material determination table showing the relationship of fig. 8.

Here, the material of the object 5 to be heated serving as a load is roughly classified into a magnetic material such as iron or ferrite stainless steel (SUS430) and a non-magnetic material such as aluminum or copper. Further, in the object 5, there is a composite body in which a magnetic body is attached to a nonmagnetic body.

Fig. 9 is a diagram showing an object to be heated of a composite body inductively heated by the induction heating cooker of embodiment 1. Fig. 9 is a view of the object 5 as viewed from the bottom.

As shown in fig. 9, the object 5 to be heated of the composite body is formed by attaching a magnetic body 6 such as stainless steel to the center of the bottom of a non-magnetic frying pan made of aluminum or the like, for example. The magnetic body 6 is attached to the nonmagnetic body by any method such as adhesion, welding, thermal spraying, pressure bonding, fitting, caulking, embedding, or the like.

In general, the magnetic body 6 is attached to the object 5 to be heated of the composite body at the central portion of the non-magnetic base body having a flat bottom surface, and the magnetic body 6 is not attached to the outer peripheral portion of the bottom surface bent. When such an object 5 to be heated is placed on the heating port, a magnetic body and a nonmagnetic body are placed above the plurality of heating coils. That is, in the material determination, as shown in fig. 8, the load characteristic of the coil in which the magnetic body and the nonmagnetic body are placed above becomes the characteristic of the "composite region" which is the region between the characteristic of the magnetic body and the characteristic of the nonmagnetic body.

The material of the load placed above the coil determined by the material determination unit 46 is the material of the load directly above the coil. For example, in the object 5 to be heated of the composite shown in fig. 9, the magnetic body 6 is placed directly above the inner peripheral coil 111, and the non-magnetic body serving as a base of the object 5 to be heated is placed further above the magnetic body 6. In this case, the material determination unit 46 determines that the material of the load placed above the inner coil 111 is a magnetic material.

Next, the control device 45 controls the drive circuits 50a to 50c based on the result of the material quality determination process, and performs a heating operation of supplying high-frequency power according to the heating power of the induction heating.

Hereinafter, the heating operation in the case where the object 5 to be heated made of the composite body is placed on the heating port of the induction heating cooker 100 and the heating operation in the case where the object 5 to be heated made of only a magnetic body is placed will be described separately.

< composite object to be heated 5>

Fig. 10 is a diagram showing a heating coil and an object to be heated in the induction heating cooker according to embodiment 1. Fig. 10 schematically shows a vertical cross section of the composite body with the object 5 placed on the heating port. In fig. 10, illustration of the top plate 4, the support table 62, and the like is omitted only from the center C of the inner coil 111, the middle coil 112, and the outer coil 113 to the right.

As shown in fig. 10, when object to be heated 5 of the composite body is placed on the heating port of induction heating cooker 100, material quality determination unit 46 determines that magnetic substance 6 is placed above inner circumferential coil 111. The material quality determination unit 46 determines that the magnetic substance 6 is placed on a part of the upper side of the intermediate coil 112 and the nonmagnetic substance is placed on the other part. That is, the material determination unit 46 determines that the material of the object 5 placed above the intermediate coil 112 is a composite body including a magnetic body and a nonmagnetic body. The material quality determination unit 46 determines that the nonmagnetic material is placed above the outer coil 113.

When the material of the object 5 placed above the inner peripheral coil 111 is a magnetic material, the material of the object 5 placed above the intermediate coil 112 includes a magnetic material and a non-magnetic material, and the non-magnetic material is placed above the outer peripheral coil 113, the controller 45 performs the following operations. The control device 45 operates the drive circuit 50a and the

drive circuits

50b and 50 c. That is, a high-frequency current is supplied to the inner circumferential coil 111, the intermediate coil 112, and the outer circumferential coil 113.

The control device 45 sets the frequency of the high-frequency current supplied from the drive circuit 50a to the inner peripheral coil 111 to a frequency set in advance corresponding to the magnetic material, for example, 25 kHz. The control device 45 sets the frequency of the high-frequency current supplied from the drive circuit 50b to the intermediate coil 112 to a frequency predetermined in accordance with the magnetic material, for example, 25 kHz. The control device 45 increases the frequency of the high-frequency current supplied from the drive circuit 50c to the outer peripheral coil 113 to be higher than the frequency of the high-frequency current supplied from the drive circuit 50a to the inner peripheral coil 111. For example, the control device 45 sets the frequency of the high-frequency current supplied from the drive circuit 50c to the outer coil 113 to a frequency corresponding to the non-magnetic material, for example, 90 kHz.

The controller 45 controls the heating power (electric power) by changing the on-duty ratio (on-off ratio) of the switching elements of the inverter circuit 23. Thereby, the object 5 to be heated disposed on the top plate 4 is inductively heated.

The reason why the frequency of the high-frequency current supplied from the drive circuit 50c to the outer circumferential coil 113 is higher than the frequency of the high-frequency current supplied to the intermediate coil 112 and the inner circumferential coil 111 is as follows.

That is, in order to inductively heat a nonmagnetic material made of aluminum or the like, it is necessary to reduce the skin depth of eddy currents generated in the object 5 to be heated, reduce the penetration volume, and increase the impedance. Therefore, by supplying a high-frequency current (for example, 75kHz to 100 kHz) to the outer peripheral coil 113 on which the nonmagnetic material is placed, the nonmagnetic material generates a high-frequency eddy current, and the object 5 can be sufficiently heated by joule heat.

On the other hand, a magnetic body made of iron or the like has a large impedance to eddy current. Therefore, even if a frequency lower than the frequency of the high-frequency current supplied to the outer peripheral coil 113 (for example, 20kHz to 35 kHz) is supplied to the intermediate coil 112 on which the composite body including the magnetic body and the nonmagnetic body is placed, the object 5 can be sufficiently heated by the joule heat generated by the eddy current.

Here, when a plurality of heating coils close to each other are simultaneously driven, interference sound corresponding to a difference between the driving frequencies may be generated. In order to suppress such interference sound, the control device 45 may set the driving frequency of the driving circuit 50c of the outer coil 113 to be higher than the driving frequency of the driving circuit 50b of the intermediate coil 112 by an audible frequency or higher (approximately 20kHz or higher). In addition to the on duty variable control, for example, when the drive frequency of the drive circuit 50c of the outer coil 113 is made variable within a predetermined range, the lower limit drive frequency of the drive circuit 50c of the outer coil 113 is set to be higher than the upper limit drive frequency of the drive circuit 50c of the intermediate coil 112 by 20kHz or more. The maximum driving frequency of the outer circumferential coil 113 is set to, for example, 100 kHz. This can suppress the generation of interference sound generated when the intermediate coil 112 and the outer coil 113 that are close to each other are simultaneously driven.

As described above, when the heating operation is performed such that the frequency of the high-frequency current supplied to the outer circumferential coil 113 is higher than the frequency of the high-frequency current supplied to the inner circumferential coil 111, an eddy current is also generated in the support base 62 made of a nonmagnetic material. That is, the magnetic flux from the outer circumferential coil 113 is interlinked with the support base 62, and an eddy current is generated in the support base 62 located below the outer circumferential coil 113.

As shown in fig. 5 to 7, a plurality of openings 63 are formed in the support base 62 below the outer circumferential coil 113. Therefore, compared to the case where the plurality of openings 63 are not formed in the support base 62, the eddy current generated in the support base 62 is reduced. In addition, compared to the case where the plurality of openings 63 are not formed in the support base 62, the flow path of the vortex generated in the support base 62 is divided by the plurality of openings 63. That is, compared to the case where the plurality of openings 63 are not formed in the support base 62, the induction heating of the support base 62 by the magnetic field from the outer circumferential coil 113 is suppressed.

< object to be heated 5 of magnetic substance >

Fig. 11 is a diagram showing a heating coil and an object to be heated in the induction heating cooker according to embodiment 1. Fig. 11 schematically shows a vertical cross section of the object 5 formed only of a magnetic material and placed on the heating port. In fig. 11, illustration of the top plate 4, the support table 62, and the like is omitted only from the center C of the inner coil 111, the middle coil 112, and the outer coil 113 to the right.

As shown in fig. 11, when the object 5 to be heated, which is formed of only a magnetic material, is placed on the heating port of the induction heating cooker 100, the material quality determination unit 46 determines that the magnetic material is placed above the inner coil 111, the intermediate coil 112, and the outer coil 113.

When the material of the object 5 placed above the inner coil 111, the intermediate coil 112, and the outer coil 113 is a magnetic material, the controller 45 performs the following operations. The control device 45 operates the drive circuits 50a to 50 c. That is, a high-frequency current is supplied to the inner circumferential coil 111, the intermediate coil 112, and the outer circumferential coil 113.

The control device 45 sets the frequency of the high-frequency current supplied from the drive circuit 50a, the drive circuit 50b, and the drive circuit 50c to a frequency predetermined in accordance with the magnetic material, for example, 25 kHz.

The controller 45 controls the heating power (electric power) by changing the on-duty ratio (on-off ratio) of the switching elements of the inverter circuit 23. Thereby, the object 5 to be heated disposed on the top plate 4 is inductively heated. Since the support base 62 disposed below the plurality of heating coils is made of a non-magnetic material, induction heating by the magnetic field from the plurality of heating coils is reduced.

As described above, embodiment 1 includes the support base 62 disposed below the plurality of heating coils. The support base 62 is formed of a flat plate of a non-magnetic material, and the support base 62 has a plurality of openings 63 formed below the outer peripheral coil 113. Therefore, when the heating operation is performed such that the frequency of the high-frequency current supplied to the outer circumferential coil 113 is higher than the frequency of the high-frequency current supplied to the inner circumferential coil 111, the induction heating of the support base 62 by the magnetic field from the outer circumferential coil 113 is suppressed. Therefore, the temperature rise of the nonmagnetic support base 62 can be suppressed. In addition, when the object 5 of the composite material is inductively heated, induction heating suitable for the material of the object 5 can be performed.

In embodiment 1, an insulator 60 is provided between the plurality of heating coils and the plurality of ferrites 61. Therefore, the electrical insulation between the plurality of heating coils and the plurality of ferrites 61 can be improved. Therefore, the distance between the plurality of heating coils and the plurality of ferrites 61 can be shortened, and the induction heating member can be reduced in size and thickness.

(modification 1)

As shown in fig. 12, the first induction heating member 11 in modification 1 includes: an insulator 60a disposed between the plurality of heating coils and the ferrite 61; and an insulator 60b disposed between the plurality of ferrites 61 and the support base 62.

With this configuration, electrical insulation between the plurality of heating coils and the support base 62 can be improved. Therefore, the distance between the plurality of heating coils and the support base 62 can be shortened, and the induction heating member can be reduced in size and thickness.

Note that, the insulator 60a disposed between the plurality of heating coils and the ferrites 61 may be omitted, and only the insulator 60b disposed between the plurality of ferrites 61 and the support base 62 may be provided.

(modification 2)

As shown in fig. 13, the support base 62 in modification 2 has a plurality of openings 64 formed below the intermediate coil 112 in addition to the plurality of openings 63 below the outer peripheral coil 113. As shown in fig. 13, the plurality of openings 64 are formed in a rectangular shape, for example. The shape of the plurality of openings 64 is not limited to a rectangle, and may be any shape such as a circle or an ellipse. In addition, the plurality of openings 64 may be provided below the ferrite 61.

With this configuration, when the heating operation is performed such that the frequency of the high-frequency current supplied to the intermediate coil 112 is higher than the frequency of the high-frequency current supplied to the inner peripheral coil 111, the induction heating of the support base 62 by the magnetic field from the intermediate coil 112 is suppressed. Therefore, the temperature rise of the nonmagnetic support base 62 can be suppressed.

Here, a specific example of the heating operation in which the frequency of the high-frequency current supplied to the intermediate coil 112 is higher than the frequency of the high-frequency current supplied to the inner peripheral coil 111 will be described with reference to fig. 14.

Fig. 14 is a diagram showing a heating coil and an object to be heated in modification 2 of the induction heating cooker according to embodiment 1. Fig. 14 schematically shows a vertical cross section of the composite body with the object 5 placed on the heating port. In fig. 14, illustration of the top plate 4, the support table 62, and the like is omitted only from the center C of the inner coil 111, the middle coil 112, and the outer coil 113 to the right.

As shown in fig. 14, when the magnetic substance 6 of the object 5 to be heated of the composite is placed only above the inner peripheral coil 111, that is, when the end of the magnetic substance 6 is positioned between the inner peripheral coil 111 and the intermediate coil 112, the controller 45 performs the following operations.

The material determination unit 46 of the control device 45 determines that the magnetic substance 6 is placed above the inner coil 111. The material quality determination unit 46 determines that the nonmagnetic material is placed above the intermediate coil 112. The material determination unit 46 determines that the outer coil 113 is unloaded.

When the material of the object 5 placed above the inner peripheral coil 111 is a magnetic material, the material of the object 5 placed above the intermediate coil 112 is a non-magnetic material, and the outer peripheral coil 113 is unloaded, the controller 45 performs the following operations. The control device 45 operates the

drive circuits

50a and 50b and stops the operation of the drive circuit 50 c. That is, the high-frequency current is supplied to the inner circumferential coil 111 and the intermediate coil 112, and the supply of the high-frequency current to the outer circumferential coil 113 is stopped.

The control device 45 sets the frequency of the high-frequency current supplied from the drive circuit 50a to the inner peripheral coil 111 to a frequency set in advance corresponding to the magnetic material, for example, 25 kHz. The control device 45 increases the frequency of the high-frequency current supplied from the drive circuit 50b to the intermediate coil 112 to be higher than the frequency of the high-frequency current supplied from the drive circuit 50a to the inner peripheral coil 111. For example, the control device 45 sets the frequency of the high-frequency current supplied from the drive circuit 50b to the intermediate coil 112 to a frequency corresponding to the non-magnetic substance, for example, 90 kHz.

By such an operation, when the object 5 to be heated of the composite body is inductively heated, induction heating suitable for the material of the object 5 can be performed. In addition, compared to the case where the plurality of openings 64 are not formed in the support base 62, the eddy current generated in the support base 62 located below the intermediate coil 112 is reduced. That is, compared to the case where the plurality of openings 64 are not formed in the support base 62, the induction heating of the support base 62 by the magnetic field from the intermediate coil 112 is suppressed.

Embodiment 2.

Hereinafter, the structure of the induction heating cooker of embodiment 2 will be mainly described focusing on the differences from embodiment 1 described above. The same components as those in embodiment 1 are denoted by the same reference numerals, and description thereof is omitted.

Fig. 16 is a plan view showing a support base and ferrite of an induction heating cooker according to embodiment 2. Fig. 15 and 16 schematically illustrate the arrangement and shape of each component.

As shown in fig. 15 and 16, the support base 62 has a plurality of cutouts 65 formed below the outer peripheral coil 113. That is, the support base 62 has an opening formed by a notch 65 provided in the outer peripheral edge. The plurality of cutouts 65 are formed in a rectangular shape, for example. The shape of the plurality of cutouts 65 is not limited to a rectangular shape, and may be any shape such as a semicircular shape or a triangular shape.

In such a configuration, as in embodiment 1, the induction heating of the support base 62 by the magnetic field from the outer circumferential coil 113 is suppressed, and the temperature rise of the support base 62 can be suppressed.

The plurality of cutouts 65 may be formed to extend from the outer peripheral edge of the support base 62 to below the intermediate coil 112. As a result, as in modification 2 of embodiment 1, induction heating of the support base 62 by the magnetic field from the intermediate coil 112 is suppressed, and a temperature rise of the support base 62 can be suppressed.

Embodiment 3.

Hereinafter, the structure of the induction heating cooker in embodiment 3 will be mainly described focusing on the differences from embodiment 1 described above. The same components as those in embodiment 1 are denoted by the same reference numerals, and description thereof is omitted.

Fig. 18 is a vertical sectional view showing a first induction heating member of an induction heating cooker according to embodiment 3. Fig. 17 and 18 schematically illustrate the arrangement and shape of each component.

As shown in fig. 17 and 18, a ferrite 61b and a plurality of ferrites 61a are disposed below the insulator 60. The plurality of ferrites 61a are formed in a rod shape, for example. For example, as shown in fig. 17, 8 ferrites 61a are disposed radially from the center of the plurality of heating coils below the inner peripheral coil 111 and the intermediate coil 112. The ferrite 61b is disposed below the outer circumferential coil 113. The ferrite 61b is formed in an annular shape having substantially the same width as the outer circumferential coil 113 in a plan view. That is, in a plan view, the area of the ferrite 61b positioned below the outer circumferential coil 113 is larger than the area of the plurality of ferrites 61a positioned below the inner circumferential coil 111.

The shape of the ferrite 61b positioned below the outer circumferential coil 113 is not limited to an annular shape, and may be any shape. That is, the ferrite 61b positioned below the outer coil 113 may be configured such that the area of the area positioned below the outer coil 113 is larger than the area of the ferrite 61a positioned below the inner coil 111 in a plan view. For example, a plurality of rod-shaped ferrites may be disposed below the outer circumferential coil 113.

With the above configuration, the high-frequency magnetic flux generated from the outer coil 113 passes through the ferrite 61b, and the magnetic flux crossing the support base 62 disposed below the ferrite 61b can be reduced. Therefore, induction heating of the support base 62 by the magnetic field from the outer circumferential coil 113 is suppressed. Therefore, the temperature rise of the nonmagnetic support base 62 can be suppressed.

In addition to the configuration of

embodiment

1 or 2, the ferrite 61b is disposed below the outer circumferential coil 113, so that leakage flux leaking from the plurality of openings 63 or the plurality of slits 65 formed in the support base 62 to below the support base 62 can be reduced.

As in modification 2 of embodiment 1, a plurality of openings 64 may be formed below the intermediate coil 112. As in embodiment 2, the plurality of cutouts 65 may be formed to extend from the outer peripheral edge of the support base 62 to below the intermediate coil 112. As a result, as in modification 2 of embodiment 1, induction heating of the support base 62 by the magnetic field from the intermediate coil 112 is suppressed, and a temperature rise of the support base 62 can be suppressed.

In embodiment 3, the plurality of openings 63, the plurality of openings 64, and the plurality of notches 65 may not be formed in the support base 62. In such a configuration, the magnetic flux crossing the support base 62 disposed below the ferrite 61b can be reduced only by the ferrite 61b, and the induction heating of the support base 62 by the magnetic field from the outer circumferential coil 113 can be suppressed. Therefore, the temperature rise of the nonmagnetic support base 62 can be suppressed.

(modification 1)

Ferrite 61b located below outer circumferential coil 113 may be made of a material having a frequency characteristic different from that of ferrite 61a located below inner circumferential coil 111. Specifically, the ferrite 61b positioned below the outer circumferential coil 113 may be made of a material having a lower magnetic resistance at high frequencies than the ferrite 61a positioned below the inner circumferential coil 111. Here, the high frequency means a frequency of the high frequency current supplied to the outer circumferential coil 113 in the heating operation in which the frequency of the high frequency current supplied to the outer circumferential coil 113 is set higher than the frequency of the high frequency current supplied to the inner circumferential coil 111. For example, the ferrite 61b has a smaller magnetic resistance with respect to a magnetic field of a frequency corresponding to the non-magnetic substance, for example, 90kHz, than the ferrite 61 a.

With this configuration, the loss of the ferrite 61b located below the outer circumferential coil 113 can be reduced. Therefore, in the heating operation in which the frequency of the high-frequency current supplied to the outer circumferential coil 113 is set higher than the frequency of the high-frequency current supplied to the inner circumferential coil 111, the temperature rise of the nonmagnetic support 62 can be further suppressed.

(modification 2)

As shown in fig. 19, ferrite 61c located below outer periphery coil 113 has a convex shape in which an end portion on the outer periphery side of outer periphery coil 113 protrudes upward along a side surface of outer periphery coil 113. That is, the ferrite 61c positioned below the outer circumferential coil 113 is formed in an L-shape in cross section.

With this configuration, the magnetic flux toward the object 5 placed on the top plate 4 is increased by the convex shape of the ferrite 61c, and the heating efficiency can be improved, as compared with the case where the convex shape is not provided. In addition, compared to the case where the convex portion shape is not provided, the magnetic flux generated from the outer circumferential coil 113 is less likely to link with the support base 62, and the temperature rise of the support base 62 can be further suppressed.

(modification 3)

As shown in fig. 20, ferrite 61d positioned below outer periphery coil 113 has a convex shape in which the end portion on the outer periphery side of outer periphery coil 113 protrudes upward along the side surface of outer periphery coil 113. The ferrite 61d positioned below the outer circumferential coil 113 has a convex shape in which an end portion on the inner circumferential side of the outer circumferential coil 113 protrudes upward along a side surface of the outer circumferential coil 113. That is, the ferrite 61d positioned below the outer circumferential coil 113 is formed in a U-shape in cross section.

With this configuration, the magnetic flux toward the object 5 placed on the top plate 4 is increased by the convex shape of the ferrite 61d, and the heating efficiency can be improved, as compared with the case where the convex shape is not provided. In addition, compared to the case where the convex portion shape is not provided, the magnetic flux generated from the outer circumferential coil 113 is less likely to link with the support base 62, and the temperature rise of the support base 62 can be further suppressed.

The convex portion may be formed only at the end portion on the inner circumferential side of the outer circumferential coil 113, and may not be formed on the outer circumferential side.

Embodiment 4.

Hereinafter, the structure of the induction heating cooker of embodiment 4 will be mainly described with respect to the differences from embodiments 1 to 3 described above. The same components as those in embodiments 1 to 3 are denoted by the same reference numerals, and description thereof is omitted.

Fig. 21 is a vertical sectional view showing a support base and a magnetism preventing member of an induction heating cooker according to embodiment 4. Fig. 21 schematically shows the arrangement and shape of each component. In fig. 21, only the main portions of the support base 62 and the magnetism preventing member 70 are shown.

As shown in fig. 21, a magnetism preventing member 70 is provided below the opening 63 of the support base 62. The magnetism preventing member 70 is disposed at a distance from the lower surface of the support base 62. The magnetism preventing member 70 is formed of a flat plate made of metal. The magnetism preventing member 70 is made of, for example, a magnetic sheet or a metal of a magnetic body.

With this configuration, the magnetic field leaking downward from the opening 63 of the support base 62 can be shielded by the magnetism preventing member 70. Therefore, the plurality of openings 63 formed in the support base 62 can suppress induction heating of the support base 62 by the magnetic field from the outer circumferential coil 113, and can reduce the leakage magnetic field leaking downward from the plurality of openings 63. Further, by reducing the magnetic field leaking to the lower side of the induction heating member, for example, the electric components such as the substrate can be disposed below the induction heating member, and the degree of freedom of the structural arrangement can be improved.

In the example of fig. 21, the antimagnetic member 70 is disposed over the entire range below the opening 63 of the support base 62, but the present invention is not limited to this. If the antimagnetic member 70 is disposed at least in a portion below the opening 63 of the support base 62, an effect of reducing a leakage magnetic field leaking downward from the plurality of openings 63 can be obtained.

(modification 1)

Fig. 23 is a perspective view showing a support base and a magnetism preventing member in modification 1 of the induction heating cooker according to embodiment 4. Fig. 22 and 23 schematically show the arrangement and shape of each component. In fig. 22 and 23, only the main portions of the support base 62 and the magnetism preventing member 75 are shown. Fig. 23 is a perspective view of the support base 62 as viewed from below.

As shown in fig. 22 and 23, the end of the magnetism preventing member 75 in modification 1 is connected to a part of the edge of the opening 63 of the support base 62. For example, the magnetism preventing member 75 is formed integrally with the support base 62 by cutting and raising the opening 63 of the support base 62. Specifically, the opening 63 of the support base 62 and the magnetism preventing member 75 are formed as follows. That is, a U-shaped slit is formed in the support base 62, and the remaining portion after the cutting is bent downward to form an L-shaped cross section, thereby integrally forming the opening 63 and the magnetism preventing member 75.

With this configuration, the magnetic field leaking downward from the opening 63 of the support base 62 can be shielded by the magnetism preventing member 75. Further, the magnetism preventing member 75 can be formed without an additional member. Therefore, reduction in manufacturing cost can be achieved.

Since the magnetism preventing member 75 in modification 1 is made of a nonmagnetic material that is the same as the material of the support base 62, an eddy current may be generated by a magnetic field leaking from the opening 63. However, since the magnetism preventing member 75 is located below the support base 62, the distance from the outer circumferential coil 113 is longer than the support base 62, and the magnetic field strength linked to the magnetism preventing member 75 is reduced. Therefore, compared to the case where the magnetism preventing member 75 is not provided, the induction heating of the support base 62 by the magnetic field from the outer circumferential coil 113 is suppressed.

(modification 2)

Fig. 24 is a vertical sectional view showing a support base and a magnetism preventing member in modification 2 of the induction heating cooker according to embodiment 4. Fig. 24 schematically shows the arrangement and shape of each component. In fig. 24, only the main portions of the support base 62 and the magnetism preventing member 75 are shown.

The case where the cross-sectional shape of the magnetism preventing member 75 of modification 1 is an L-shape was described, but the present invention is not limited thereto. For example, as shown in fig. 24, the magnetism preventing member 75 is formed by forming a U-shaped slit in the support base 62, bending the remaining portion of the slit downward to form a V-shaped cross section, and integrally forming the opening 63 and the magnetism preventing member 75.

Even in such a shape, the same effects as in modification 1 can be obtained.

(modification 3)

Fig. 25 is a perspective view showing a support base and a magnetism preventing member in modification 3 of the induction heating cooker according to embodiment 4. Fig. 25 schematically shows the arrangement and shape of each component. In fig. 25, only the main portions of the support base 62 and the magnetism preventing member 75 are shown. Fig. 25 is a perspective view of the support base 62 as viewed from below.

The description has been given of the case where the antimagnetic member 75 of modification 1 and modification 2 is formed by forming a U-shaped slit in the support base 62 and bending the cut-off portion downward to form the opening 63 and the antimagnetic member 75 integrally. For example, as shown in fig. 25, the magnetism preventing member 75 is formed by forming linear slits in parallel in 2 positions of the support base 62, and forming the opening 63 and the magnetism preventing member 70 in a single body by deforming a portion between the 2 linear slits in the 2 positions downward to have a trapezoidal cross section.

Even in such a shape, the same effects as in modification 1 can be obtained.

Embodiment 5.

Hereinafter, the structure of the induction heating cooker of embodiment 5 will be mainly described with respect to the differences from embodiments 1 to 4 described above. The same components as those in embodiments 1 to 4 are denoted by the same reference numerals, and description thereof is omitted.

In embodiments 1 to 4, the structure in which the inner coil 111, the intermediate coil 112, and the outer coil 113 are arranged concentrically has been described, but the number and arrangement of the heating coils are not limited to this. Specific examples will be described below.

As shown in fig. 26, the first induction heating member 11 has: an inner peripheral coil 111 disposed at the center of the first induction heating port 1; and an outer coil 113 disposed on the outer peripheral side of the inner coil 111. The inner peripheral coil 111 is driven and controlled by the drive circuit 50 a. In addition, the outer circumferential coil 113 is driven and controlled by the drive circuit 50 c. That is, the first induction heating member 11 in embodiment 5 is configured without providing the intermediate coil 112 and the drive circuit 50 b.

When the material of the object 5 placed above the inner circumferential coil 111 is a magnetic material and a non-magnetic material is placed above the outer circumferential coil 113, the controller 45 performs the following operations. The control device 45 makes the frequency of the high-frequency current supplied from the drive circuit 50c to the outer circumferential coil 113 higher than the frequency of the high-frequency current supplied from the drive circuit 50a to the inner circumferential coil 111.

In such a configuration, even when the object 5 of the composite material is inductively heated, induction heating suitable for the material of the object 5 can be performed.

(modification 1)

As shown in fig. 27, the first induction heating member 11 has: an inner peripheral coil 111 disposed at the center of the first induction heating port 1; and outer coils 113a to 113d arranged on the outer peripheral side of the inner coil 111.

The inner peripheral coil 111 includes a first inner peripheral coil 111a and a second inner peripheral coil 111b arranged concentrically. The first inner peripheral coil 111a and the second inner peripheral coil 111b are connected in series. The outer coils 113a to 113d each have a planar shape of an approximately 1/4 circular arc (banana-shaped or cucumber-shaped) and are arranged outside the inner coil 111 so as to substantially follow the outer periphery of the inner coil 111. The outer coils 113a to 113d are supplied with high-frequency currents from the drive circuit 50c, respectively.

When the material of the object 5 placed above the inner peripheral coil 111 is a magnetic material and a non-magnetic material is placed above the outer peripheral coils 113a to 113d, the controller 45 performs the following operations. The control device 45 increases the frequency of the high-frequency current supplied from the drive circuit 50c to the outer circumferential coils 113a to 113d to be higher than the frequency of the high-frequency current supplied from the drive circuit 50a to the inner circumferential coil 111.

(modification 2)

As shown in fig. 28, the intermediate coil 112 has a first intermediate heating coil 112a and a second intermediate heating coil 112 b. The first intermediate heating coil 112a and the second intermediate heating coil 112b have different diameters and are arranged concentrically. The second intermediate heating coil 112b is disposed outside the first intermediate heating coil 112 a. The first intermediate heating coil 112a and the second intermediate heating coil 112b are independently wound.

The first intermediate heating coil 112a is drive-controlled by the drive circuit 50b 1. In addition, the second intermediate heating coil 112b is drive-controlled by the drive circuit 50b 2. The configurations of the drive circuits 50b1 and 50b2 are the same as those in embodiment 1.

The controller 45 controls the frequency of the high-frequency current supplied from the drive circuit 50b1 to the first intermediate heating coil 112a according to the material of the object 5 placed above the first intermediate heating coil 112 a. The controller 45 controls the frequency of the high-frequency current supplied from the drive circuit 50b2 to the second intermediate heating coil 112b, depending on the material of the object 5 placed above the second intermediate heating coil 112 b.

Description of the reference numerals

1a first induction heating port, 2a second induction heating port, 3a third induction heating port, 4a top plate, 5 an object to be heated, 6 a magnetic body, 11a first induction heating member, 12a second induction heating member, 13a third induction heating member, 21 a.c. power supply, 22 d.c. power supply circuit, 22a diode bridge, 22b reactor, 22c smoothing capacitor, 23 inverter circuit, 23a IGBT, 23b IGBT, 23c diode, 23d diode, 24a resonant capacitor, 25a input current detection member, 25b coil current detection member, 40 operation section, 41 display section, 43 operation display section, 45 control device, 46 material determination section, 48 memory, 50 drive circuit, 50a drive circuit, 50b1 drive circuit, 50b2 drive circuit, 50c drive circuit, 60 insulator, 60a insulator, 60b insulator, and, 61 ferrite, 61a ferrite, 61b ferrite, 61c ferrite, 61d ferrite, 62 support, 62a ring, 63 opening, 64 opening, 65 notch, 70 antimagnetic member, 75 antimagnetic member, 100 induction heating cooker, 111 inner coil, 111a first inner coil, 111b second inner coil, 112 middle coil, 112a first middle heating coil, 112b second middle heating coil, 113 outer coil, 113a outer coil, 113b outer coil, 113c outer coil, 113d outer coil.

Claims

1. An induction heating cooker, comprising:

a plurality of heating coils including an inner circumferential coil disposed on an innermost circumferential side and an outer circumferential coil disposed on an outermost circumferential side;

a support base disposed below the plurality of heating coils and supporting the plurality of heating coils;

a plurality of inverter circuits that supply high-frequency power to the plurality of heating coils, respectively; and

a control device that controls driving of the plurality of inverter circuits and performs a heating operation in which a frequency of the high-frequency current supplied to the outer-periphery coil is higher than a frequency of the high-frequency current supplied to the inner-periphery coil,

the support base is formed of a flat plate of a non-magnetic material, and a plurality of openings are formed in the support base below the outer peripheral coil.

2. The induction heating cooker as claimed in claim 1,

the plurality of heating coils includes an intermediate coil disposed between the inner peripheral coil and the outer peripheral coil,

the control device performs a heating operation in which the frequency of the high-frequency current supplied to the intermediate coil is higher than the frequency of the high-frequency current supplied to the inner peripheral coil,

the support base has a plurality of openings formed below the intermediate coil.

3. The induction heating cooker as claimed in claim 1 or 2,

the opening of the support table is formed by a cutout provided in an outer peripheral edge.

4. An induction heating cooker as claimed in any one of claims 1 to 3,

the induction heating cooker includes a plurality of ferrites disposed between the plurality of heating coils and the support base,

the plurality of ferrites have a larger area in a region located below the outer circumferential coil than in a region located below the inner circumferential coil in a plan view.

5. The induction heating cooker according to any one of claims 1 to 4,

the ferrite located below the outer circumferential coil has a smaller magnetic resistance at a frequency of a high-frequency current supplied to the outer circumferential coil than a magnetic resistance of the ferrite located below the inner circumferential coil.

6. The induction heating cooker as claimed in claim 4 or 5,

an end portion of the ferrite located below the outer circumferential coil on an outer circumferential side of the outer circumferential coil protrudes upward along a side surface of the outer circumferential coil.

7. The induction heating cooker as claimed in any one of claims 4 to 6,

an end portion of the ferrite located below the outer circumferential coil, the end portion being located on an inner circumference of the outer circumferential coil, protrudes upward along a side surface of the outer circumferential coil.

8. The induction heating cooker as claimed in any one of claims 4 to 7,

the induction heating cooker includes an insulator disposed between the plurality of heating coils and the ferrite.

9. The induction heating cooker as claimed in any one of claims 4 to 7,

the induction heating cooker includes an insulator disposed between the plurality of ferrites and the support base.

10. The induction heating cooker according to any one of claims 1 to 9,

the induction heating cooker is provided with a magnetism preventing member which is arranged below the opening of the support base and is composed of a metal flat plate.

11. The induction heating cooker as claimed in claim 10,

an end of the antimagnetic member is connected to a part of an edge of the opening.

12. The induction heating cooker as claimed in claim 11,

the antimagnetic member is integrally formed with the support base by cutting and raising the opening of the support base.

13. The induction heating cooker as claimed in any one of claims 1 to 12,

the plurality of heating coils have different diameters and are arranged concentrically.

14. The induction heating cooker as claimed in any one of claims 1 to 13,

the induction heating cooker is provided with a material determination unit for determining the material of the object to be heated placed above each of the plurality of heating coils,

when the material of the object to be heated placed above the outer peripheral coil is a material including at least a non-magnetic body, and the material of the object to be heated placed above the inner peripheral coil is a magnetic body, the control device increases the frequency of the high-frequency current supplied to the outer peripheral coil relative to the frequency of the high-frequency current supplied to the inner peripheral coil.